Preprint published in Applied Thermal EngineeringPavement-watering as a technique of cooling dense urban areas and reducing the urban heat island effect has been studied since the 1990's. The method is currently considered as a potential tool for and climate change adaptation against increasing heat wave intensity and frequency. However, although water consumption necessary to implement this technique is an important aspect for decision makers, optimization of possible watering methods has only rarely been conducted. We propose an analysis of pavement heat flux at a depth of 5 cm and solar irradiance measurements to attempt to optimize the watering period, cycle frequency and water consumption rate of a pavement-watering method applied in Paris over the summer of 2013. While fine-tuning of the frequency can be conducted on the basis of pavement heat flux observations, the watering rate requires a heat transfer analysis based on a relation established between pavement heat flux and solar irradiance during pavement insolation. From this, it was found that watering conducted during pavement insolation could be optimized to a frequency of every 30 minutes and water consumption could be reduced by more than 76% while reducing the cooling effect by less than 10%

Urban heat island (UHI) countermeasures are of growing interest for cities. Field studies of their micro-climatic effects are scarce, yet are essential to properly evaluate their effectiveness and that of anti-UHI policies. The standard approach to determining their micro-climatic effects is to study the difference in measurements made at case and control stations. However, measurements conducted during a pavement-watering experiment in Paris, France reveal that this method mistakes preexisting differences for pavement-watering effects. An alternative approach based on a twosample t-test was therefore developed and tested with the pavement-watering field trial as a case study. The proposed method proved able to determine the effects of pavement-watering, without misinterpreting preexisting differences. In the process of the case study, watering was found to reduce maximum daily heat stress, while having smaller statistically significant UHI-reducing effects. The greatest effects were reached during the day for all parameters with maximum reductions of 0.79°C, 1.76°C and 1.03°C for air, mean radiant and UTCI-equivalent temperatures and a 4.1% increase in relative humidity, while UHI-mitigation reached up to-0.22°C. The methodology developed is not specific to pavement-watering and recommendations for its improvement and its application to the field-evaluation of other UHI countermeasures are made.

Les collectivités territoriales s’engagent dans de nombreuses actions pour limiter leurs impacts environnementaux. La ville de Paris cherche à se doter de nouveaux outils permettant de mesurer l’incidence de choix urbains ou architecturaux sur l’environnement dès la phase de conception. Les outils d’analyse du cycle de vie (ACV) permettent aujourd’hui d’évaluer les performances tout au long de la vie d’un ouvrage : construction, exploitation, fin de vie. La recherche présentée dans cet article a permis d’effectuer l’ACV de la ZAC Claude Bernard à Paris et d’observer le potentiel d’aide à la décision pour la maitrise d’ouvrage d’un tel outil.Local authorities are engaged in numerous actions in favor of the environment. The City of Paris is interested in new tools to take into account environmental impacts of their urban planning projects during the different stages of the project design. Life Cycle Assessment (LCA) tools allow environmental impacts of a building to be evaluated during its life: construction, exploitation, end of life. In this article, we test an LCA tool on an urban planning project in Paris (France) in order to analyze the relevance of LCA for assessing district impacts and being a decision support tool

Published in Urban ClimatePavement-watering has been studied since the 1990's and is currently considered a promising tool for urban heat island reduction and climate change adaptation. However, possible future water resource availability problems require that water consumption be optimized. Although pavement heat flux can be studied to improve pavement-watering methods (frequency and water consumption), these measurements are costly and require invasive construction work to install appropriate sensors in a dense urban environment. Therefore, we analyzed infrared camera measurements of pavement surface temperatures in search of alternative information relevant to this goal. Firstly, surface temperature reductions of up to 4°C during shading and 13°C during insolation were found. Secondly, the infrared camera successfully detected temperature spikes indicative of surface drying and can therefore be used to optimize the watering frequency. Measurements made every 5 min or less are recommended to minimize relevant data loss. Finally, if the water retaining capacity of the studied pavement is known, optimization of total water consumption is possible on the sole basis of surface temperature measurements

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